Importance of Insectivorous Birds

For the first time, the predation impact of the insectivorous birds has been quantified on a global scale based on 103 (for the most part published) studies of prey consumption (kg per ha per season) of insectivorous birds in seven terrestrial biome types (i.e., tropical forests, temperate/boreal forests, tropical grasslands/savannas, temperate grasslands, croplands, deserts, and Arctic tundra).

By extrapolation, we estimate the biomass of arthropod prey consumed by the world’s insectivorous birds to be somewhere between 400 and 500 million tons per year, but most likely at the lower end of this range. If this figure is converted to an energy measure, it turns out that insectivorous birds have an energy consumption of ≈2.7 Exajoules per year (or ≈0.15% of the global terrestrial net primary production).

Birds in forests account for roughly 75% of the global annual prey consumption (≈300 million tons per year), whereas birds in the other biomes are less significant contributors (combined ≈100 million tons per year). Especially during the breeding season, when adult birds feed their nestlings protein-rich prey, billions of herbivorous insects (including large numbers of potentially harmful beetles and caterpillars) are captured. The estimates presented in this paper emphasize the ecological and economic importance of insectivorous birds in suppressing potentially harmful insect pests on a global scale – especially in forested areas.

Insectivorous birds are a group of endangered animals heavily threatened by factors such as afforestation, logging of trees in urban, suburban and rural areas, intensification of agriculture, the spread of systemic pesticides, light pollution, collision with man-made structures, predation by feral cats, hunting of migrating birds by the Mediterranean people etc. If these global threats cannot soon be resolved, we must fear that the vital pest suppression ecosystem services, that insectivorous birds provide, will get lost.

Red-backed Shrike with a Grasshopper to feed to its fledglings. Photo: Per Ekberg, Gribskov 2018